Carotid sheath with entry and tracking rapid exchange dilators and method of use

ABSTRACT

Dilators and sheaths for use in minimally invasive vascular therapy are disclosed. In some embodiments, the dilators include a slot that accesses a guidewire lumen within the dilator. These slots facilitate rapid exchange of one dilator for another. In another embodiment, a dilator is sufficiently stiff to facilitate entry, but also designed to facilitate placement of the dilator along a tortuous path.

RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 13/349,060 filed on Jan. 12, 2012 and titled CAROTID SHEATHWITH ENTRY AND TRACKING RAPID EXCHANGE DILATORS AND METHOD OF USE, whichis hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to minimally invasive treatmentdevices such as sheaths, catheters, and dilators. More specifically, thepresent disclosure relates to sheaths, catheters, and dilators for usewith treatments within the human vasculature, including the carotidartery.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments disclosed herein will become more fully apparent fromthe following description and appended claims, taken in conjunction withthe accompanying drawings. These drawings depict only typicalembodiments, which will be described with additional specificity anddetail through use of the accompanying drawings in which:

FIG. 1 is a longitudinal cross section of portions of one embodiment ofa rapid exchange entry dilator and a carotid sheath.

FIG. 2 is a longitudinal cross section of one embodiment of a rapidexchange tracking dilator disposed within a carotid sheath.

FIG. 3 is a transverse cross sectional view of the tracking dilator ofFIG. 2, taken through line 3-3.

FIG. 4 is a transverse cross sectional view of the tracking dilator ofFIG. 2, taken through line 4-4.

FIG. 5 is a longitudinal cross section of a dilator disposed within acarotid sheath.

FIG. 6 is a transverse cross sectional view of a portion of the dilatorof FIG. 5, taken through line 6-6.

FIG. 7 is a transverse cross sectional view of a portion of the dilatorof FIG. 5, taken through line 7-7.

DETAILED DESCRIPTION

Catheters, sheaths, dilators, guidewires, and other treatment devicesare used in connection with minimally invasive treatments and therapies,such as minimally invasive therapies within the human vasculature. Thedisclosure below relates specifically to, among other things, theplacement and use of such devices to access and treat stenosis or otherobstructions within the carotid artery. Notwithstanding these specificexamples and references, the current disclosure is applicable to anytreatment involving disposition of elongate devices within body lumens.

In some procedures, stents, balloons, filters, or other treatmentdevices are advanced within the vasculature of a patient through use ofelongate catheters or sheaths. Furthermore, such sheaths or catheterscan be placed, advanced, retracted, or moved in connection with dilatorsand/or guidewires. Specifically, in some instances, an elongate sheathor guiding catheter is disposed within the vasculature such that itsdistal end accesses a portion of the carotid artery. Such a sheath orguiding catheter may be designed to provide therapy within thevasculature or may be used as a conduit to advance other instruments,for example a catheter containing a stent or other treatment device, tothe treatment site. In some instances, the sheath or guiding catheter isplaced and positioned through use of dilators and/or guidewires. As usedherein, a “carotid sheath” refers to a sheath or catheter configured toprovide access to the carotid artery.

It will be readily understood that the components of the embodiments, asgenerally described and illustrated in the figures herein, could bearranged and designed in a variety of configurations. Thus, thefollowing more detailed description of various embodiments, asrepresented in the figures, is not intended to limit the scope of thedisclosure, but is merely representative of various embodiments. Whilethe various aspects of the embodiments are presented in drawings, thedrawings are not necessarily drawn to scale unless specificallyindicated.

The phrases “connected to,” “coupled to,” and “in communication with”refer to any form of interaction between two or more entities, includingmechanical, electrical, magnetic, electromagnetic, fluid, and thermalinteraction. Two components may be coupled to each other even thoughthey are not in direct contact with each other. For example, twocomponents may be coupled to each other through an intermediatecomponent.

The terms “proximal” and “distal” refer to opposite ends of a medicaldevice. As used herein, the proximal end of a medical device is the endnearest a practitioner while the practitioner is using or manipulatingthe device, while the distal end is the opposite end. For example, theproximal end of a catheter or sheath used in minimally invasive vasculartreatment is the end accessible to a practitioner during use, while thedistal end is disposed within a patient during use.

The “axial direction” of an elongate component refers to a directionalong the center axis of the elongate component.

In some instances, a practitioner accesses the carotid artery by anentry point in the femoral artery. A relatively small catheter and/orguidewire can then be advanced from the femoral artery to the aorticarch, and from the aortic arch to either the right or left commoncarotid artery (in some instances via the innominate artery in the caseof the right common carotid artery). Access to the internal or externalcarotid arteries is generally gained via either common carotid artery.The initial catheter and/or guidewire can then be used to help positionsubsequent stiffer catheters or guidewires.

An access path from the aortic arch to either common carotid artery, andany subsequent branch thereof, can be relatively tortuous. In someinstances, carotid sheaths configured to act as conduits for stentdelivery devices are relatively stiff and thus difficult to positionwithin this tortuous path. Inability to properly place a carotid sheathcan make minimally invasive stenting impossible, thus resulting in moreinvasive procedures such as surgical endarterectomy.

An exemplary procedure includes first gaining access to the vascularsystem through the femoral artery at the groin. In some instances, aneedle and/or a guidewire is utilized at this step. A physician thenadvances a guidewire and/or a diagnostic catheter (e.g., a smallcatheter size 5 or 6 French) from the entry point to the aortic arch,then from the aortic arch to the common carotid artery. In someinstances, the guidewire and/or diagnostic catheter is further advancedinto the internal or external carotid arteries. The diagnostic cathetercan then be utilized to advance a stiff guidewire to the treatment site.During the course of some procedures, the distal end of the stiffguidewire remains anchored in one of these distal positions during thetreatment. In an exemplary procedure, a physician then uses an entryand/or a tracking dilator to introduce and advance a sheath into theentry point and to a position just proximal of the treatment location.Such positioning of the sheath allows a practitioner to utilize thesheath to advance treatment devices, such as balloons, stents, and soon, to the treatment site. In some instances, the sheath is very stiff.In such instances, use of a tracking dilator to advance the relativelystiff sheath can reduce the risk that the sheath will cause the distalend of the stiff guidewire to become displaced from its anchor location.

As further described below, in some embodiments, one or more dilatorsare utilized in connection with advancing a carotid sheath to atreatment location. As used herein, “dilator” refers to an elongateinstrument that may be configured to be disposed within an elongatesheath, the dilator configured to guide the sheath as the sheath isadvanced along a path. In some embodiments, the dilator is relativelystiff or resilient to aid in advancing the dilator and/or sheath beyondpoints of high resistance, such as through an arterial wall at theaccess point (for example, in instances where scar tissue orcalcification make access particularly difficult). Some dilators includelumens configured to accommodate other instruments such as guidewires.Moreover, in certain of the embodiments described below, a dilatorincludes features configured to facilitate rapid exchange betweendilators. For instance, as detailed below, some dilators within thescope of this disclosure include a slot to facilitate rapid exchange.Rapid exchange is utilized, for example, in instances where a firstdilator is used primarily for entry (an “entry dilator”), while a seconddilator is used to advance a sheath along a distal tortuous path, suchas from the aortic arch to the carotid artery (a “tracking dilator”).

FIG. 1 is a longitudinal cross section of portions of one embodiment ofa rapid exchange entry dilator 10 and a carotid sheath 40. Asillustrated, the distal end of each component is positioned to the leftof the proximal end. In the illustrated embodiment, only a portion(adjacent the distal ends) of each component is shown, as indicated bythe cut-away lines on the right side of the drawing.

The illustrated entry dilator 10 includes an elongate main body 21configured to be disposed within the carotid sheath 40. The carotidsheath 40 is configured with a radiopaque marker band 42, which in someembodiments is positioned at or adjacent the distal end of the carotidsheath 40. The entry dilator 10 of FIG. 1 further includes a centrallumen 22 configured to accommodate a guidewire (not shown). In someembodiments the central lumen 22 is sized to accommodate particularsizes of guidewires, such as guidewires from about 0.012 inches to about0.038 inches, including guidewires from about 0.018 inches to about0.032 inches and from about 0.022 inches to about 0.028 inches.

In some embodiments the entry dilator 10 and the carotid sheath 40 aredisplaceable with respect to each other in the axial direction of eachcomponent. During certain therapies, however, the two components areadvanced or retracted within the vasculature together, meaning the twocomponents are moved as a unit, without axial displacement with respectto each other. Additionally, some instances, the two components areadvanced by a combination of moving the components together anddisplacing them with respect to each other.

In embodiments where the entry dilator 10 and the carotid sheath 40 areadvanced together, distance L1 is the length of the portion of the entrydilator 10 that extends from the distal end of the carotid sheath 40. Insome embodiments L1 is from about 2 cm to about 8 cm in length,including lengths from about 3 cm to about 7 cm and lengths from about 4cm to about 6 cm. Because, in certain embodiments, the entry dilator 10is displaceable with respect to the carotid sheath 40, distance L1 maynot be a constant value, but rather represent a general parameter. Inother embodiments, L1 represents the maximum distance the entry dilator10 is configured to extend from the carotid sheath 40. In other words,in some examples, the entry dilator 10 is configured to be displaceablewith respect to the carotid sheath 40, up to a certain point, but canfurther include a coupling mechanism (e.g., a luer fitting on theproximal end) configured to limit the maximum displacement of the distalend of the entry dilator 10 with respect to the carotid sheath 40.

In some embodiments, the entry dilator 10 includes an eccentricallylocated slot 23. (A transverse cross sectional view of an analogous slotin another embodiment of a dilator is also shown in FIG. 4.) As furtheroutlined below, the slot 23 of FIG. 1 is configured to facilitate rapidexchange of the entry dilator 10 with another dilator. In theillustrated embodiment, the slot 23 is configured as an elongate openingin the sidewall of the entry dilator 10 that is in communication withthe central lumen 22. The slot 23 extends to the proximal end of theentry dilator 10. Distance L2 shown in FIG. 1 represents the distancefrom the distal end of the carotid sheath 40 to the beginning of theslot 23. In other words, L2 is the length of the entry dilator 10 thatis disposed within the carotid sheath 40 but does not include the slot23. In some embodiments L2 is from about 5 cm to about 15 cm, includingembodiments from about 7 cm to about 12 cm and from about 9 cm to about11 cm.

The illustrated entry dilator 10 has a tapered portion 24 adjacent thedistal end of the entry dilator 10. In some embodiments the taperedportion 24 is configured to extend completely from the carotid sheath40; that is, in some embodiments the tapered portion 24 has a length ofL1. In other embodiments the tapered portion 24 is longer or shorterthan L1.

In the illustrated embodiment, distance L3 corresponds to the length ofthe entry dilator 10 and carotid sheath 40 from the distal end of theslot 23 to the proximal end (not shown) of the carotid sheath 40. Insome embodiments the entry dilator 10 extends proximally from theproximal end of the carotid sheath 40, while in other embodiments it isflush with or shorter than the carotid sheath 40 at the proximal end. Insome embodiments L3 is from about 60 to 100 cm, including embodimentsfrom about 70 cm to 90 cm and embodiments from about 75 cm to about 85cm. In certain embodiments, the carotid sheath 40 includes a luerfitting at the proximal end, including luers that are coupleable to aTouhy-Borst fitting.

In the illustrated embodiment, entry dilator 10 is configured tofacilitate entry into the vasculature. For example, in some embodimentsentry dilator 10 is relatively stiff (compared to, for example, thetracking dilator described below) in order to facilitate entry throughcalcified arteries, such as the femoral artery. In certain embodiments,the entry dilator 10 is thus composed of a relatively stiff material,for example, polypropylene or nylon. Moreover, in some embodiments thematerial used for the dilator has a durometer hardness equal to orgreater than 50 on the Shore D scale, including materials having ahardness from about 50 to about 80 on the Shore D scale, or materialshaving a hardness from about 60 to about 70 on the Shore D scale.

FIG. 2 is a longitudinal cross section of a tracking dilator 30 disposedwithin a carotid sheath 60. While FIG. 1 illustrates the entry dilator10 and FIG. 2 illustrates the tracking dilator 30, certain elements andsubcomponents of each can, in certain respects, resemble elements andsubcomponents of the other. It will be appreciated that all theillustrated embodiments may have analogous features. Accordingly, therelevant descriptions of such features apply equally to the features ofthe tracking dilator 30 and the related components of FIG. 2. Anysuitable combination of the features, and variations of the same,described with respect to the components illustrated in FIG. 1 can beemployed with the components of FIG. 2, and vice versa. Furthermore,analogous or substantially analogous features shown in one figure may ormay not be designated by a reference numeral regardless of whether theanalogous feature is so designated in the analogous figure. This patternof disclosure applies equally to further embodiments and componentsdescribed herein.

FIG. 2 shows the tracking dilator 30 disposed within a carotid sheath60. As with the carotid sheath 40 of FIG. 1, the carotid sheath 60 ofFIG. 2 includes a radiopaque marker band 62. In the illustratedembodiment, the tracking dilator 30 includes a main body 31 with acentral lumen 32 disposed within the main body 31. In some embodiments,the central lumen 32 is configured to accommodate a guidewire, analogousto the central lumen 22 of FIG. 1. Furthermore, the tracking dilator 30shown in FIG. 2 includes an eccentrically placed slot 33. In theillustrated embodiment, the slot 33 is located a distance, L6, from thedistal end of the carotid sheath 60. In some embodiments L6 is fromabout 60 to 100 cm, including embodiments from about 70 cm to 90 cm andembodiments from about 75 cm to about 85 cm. Like the slot 23 of FIG. 1,the slot 33 of the tracking dilator 30 of FIG. 2 extends from theposition shown to the proximal end (not shown) of the tracking dilator30.

As further detailed below, in some embodiments, the tracking dilator 30is configured to facilitate access to relatively tortuous portions ofthe vasculature. For example, in some procedures, a relativelysmall-diameter needle is inserted into the femoral artery at the accesspoint and a thin guidewire is inserted through the needle. In theexemplary procedure, the needle is then removed and an entry dilator(such as 10 from FIG. 1) is advanced along the guidewire. As describedabove, the entry dilator 10 of FIG. 1 is relatively stiff, allowing itto be forced through the artery wall or through calcified tissue in theartery, thereby providing fuller access to the vasculature. In someinstances the entry dilator 10 is then exchanged for the trackingdilator 30 in order to traverse tortuous paths within the vascular, forexample, traversing from the aortic arch to the common carotid artery orbeyond. In some procedures, the carotid sheath 40 is advanced with thetracking dilator 30.

In some embodiments, the slot 23, 33 of the dilator 10, 30 facilitatesrapid exchange of one dilator 10, 30 for another. For example, in someprocedures where a practitioner wishes to replace dilator “A” disposedwithin the body with dilator “B,” slots on each dilator facilitate thisexchange. In this example, a guidewire is disposed within dilator A. Ifdilator A were to be removed over the proximal end of the guidewire, thelength of guidewire disposed outside the body would need to be longerthan the total length of dilator A, in order to allow a practitioner toremove the dilator while still being able to directly grasp (orotherwise secure) the guidewire. A slot in the dilator, however, allowsthe practitioner to decouple the dilator from the guidewire via theslot, allowing the practitioner to maintain direct contact with theguidewire near the insertion point. Only the distal-most portion ofdilator A (having no slot) would need to be fed over the proximal end ofthe guidewire. Similarly, when the practitioner replaces dilator A withdilator B, the distal end (having no slot) of dilator B can be slid overthe proximal end of the guidewire while the rest of the dilator could befed onto the guidewire via the slot. Thus, as long as the guidewireextends from the patient a distance greater than the length of thenon-slotted portions of each dilator, a practitioner can quicklyexchange dilators while maintaining secure contact with the guidewirenear the insertion point.

The features of tracking dilator 30 of FIG. 2 are configured tofacilitate advancement of the tracking dilator 30 along relativelytortuous paths. In some embodiments, the tracking dilator 30 includes acylindrical portion 35 adjacent the distal end of the tracking dilator30. The cylindrical portion 35 defines a constant outside diameter alongits length, L5. L5 is from about 3 cm to about 15 cm in someembodiments, including embodiments from about 5 cm to about 12 cm andembodiments from about 7 cm to about 11 cm. Furthermore, in someembodiments, the cylindrical portion 35 is formed in a relatively thinwalled design, the wall of the dilator being less than 0.025 inches insome instances, including wall thicknesses of less than 0.020 inches,less than 0.015 inches, and less than 0.010 inches. Moreover, thetracking dilator 30 of some embodiments is composed of a relatively softmaterial, for example an elastomer with a durometer hardness that isless than or equal to 45 on the Shore D scale. In some instances, thetracking dilator 30 is softer than, for example, an entry dilator, suchas the entry dilator 10 of FIG. 1, or a carotid sheath, such as thecarotid sheathes 40, 60 of FIGS. 1 and 2.

In certain procedures, the softness of the tracking dilator 30 and/orthe thin walled design of the cylindrical portion 35 facilitatesadvancement of the tracking dilator along a tortuous path. Stifferdilators, for example the entry dilator 10 of FIG. 1, may be moredifficult to advance over relatively tortuous paths. Furthermore, thedesign of the tracking dilator 30 may lower the risk of displacing thedistal end of a guidewire used to place the tracking dilator 30, ascompared to stiffer dilators.

In some embodiments, the tracking dilator 30 includes a tapered portion34 adjacent the cylindrical portion 35. In the illustrated embodiment,the tapered portion 34 is configured as a transition portion between themore pliable cylindrical portion 35 and the stiffer proximal portion ofthe tracking dilator 30. In the exemplary embodiment, the trackingdilator 30 thus has a pliable tip to facilitate advancement of thetracking dilator 30 along a difficult path while also having a stifferportion along the length of the tracking dilator 30. This stifferportion is configured to facilitate in advancing the relatively stiffcarotid sheath 60 to the treatment location. In some embodiments, thetapered portion 34 has a length, L4, from about 5 cm to about 30 cm,including lengths from about 10 cm to about 20 cm and from about 12 cmto about 17 cm. Furthermore, in some embodiments the tapered portion 34is tapered along its entire length or is cylindrical along a portion ofits length and tapered along another portion of its length.

In some embodiments, the tracking dilator 30 is formed of a radiopaquematerial, for example an elastomeric material with tungsten particlesdeposited therein. Similarly, the entry dilator 10 of FIG. 1 is formedof a radiopaque material in some embodiments.

FIG. 3 is a transverse cross sectional view of the tracking dilator 30of FIG. 2, taken through line 3-3. This view illustrates the sidewall ofthe tracking dilator 30 in the tapered portion 34. In some embodiments,the central lumen 32 is located substantially along the central axis ofthe tracking dilator 30. Similarly, in some embodiments, the centrallumen 22 of the entry dilator 10 of FIG. 1 is located along the centralaxis of the entry dilator 10.

FIG. 4 is a transverse cross sectional view of the tracking dilator 30of FIG. 2, taken through line 4-4. FIG. 4 illustrates the position ofthe slot 33 within the main body 31 of the tracking dilator 30. FIG. 4also shows the axial positioning of the tracking dilator 30 within thecarotid sheath 60. FIG. 4 illustrates how, in some embodiments, the slot33 is eccentrically positioned within the main body 31 of the trackingdilator 30. As also shown in FIG. 2, the slot 33 of the illustratedembodiment is in communication with the central lumen 32. Therelationship between the slot 33 and the central lumen 32 may beunderstood as the central lumen 32 extending the entire length of thetracking dilator 30, with the central lumen 32 radially centered nearthe distal tip of the tracking dilator 30 and eccentrically positionedsuch that the central lumen 32 crosses the sidewall to the outsidesurface of the dilator (forming the slot 33) along the remaining lengthof the tracking dilator 30. Thus, the portion of the central lumen 32that forms the slot 33 is only a partial lumen, as it is an open, orslotted, portion. In other embodiments the central lumen 32 is radiallycentered along the length of the tracking dilator 30, with the slot 33extending from the central lumen 32 through the sidewall of the trackingdilator 30. The slot 23 of the entry dilator 10 of FIG. 1 may besimilarly positioned as described in each embodiment described inconnection with the slot 33 and the tracking dilator 30 of FIG. 2.

An exemplary procedure utilizing the entry and tracking dilators 10, 30described in connection with FIGS. 1-4 begins by a physician firstgaining access to the vascular system through the femoral artery at thegroin. In some instances, a needle and a thin guidewire are used toinitially pierce the wall of the artery. In this example, the thinguidewire is then used to advance a diagnostic catheter and/or a stiffguidewire to the treatment site. The physician then advances the entrydilator 10 along the stiff guidewire, the entry dilator 10 configured topush through calcified tissue at the entry site. In some instances thestiff guidewire extends all the way to, or beyond, a treatment site; forexample, it may be anchored in the internal or external carotidarteries. Further, in some instances, the thin guidewire is initiallyadvanced to, or beyond, the treatment site, and obviates the need for astiff guidewire.

In this example, the guidewire and/or the entry dilator 10 is then usedto advance the carotid sheath 40 such that it provides access to thetreatment site. In some embodiments the distal end of the carotid sheath40 will be positioned just proximal to the treatment site. In someinstances, the carotid sheath 40 is relatively stiff, such thatadvancing the carotid sheath 40 along the guidewire poses a significantrisk the guidewire will become displaced or dislodged, includinginstances where the distal end of the guidewire is moved from its anchorlocation. Thus, in some embodiments, the entry dilator 10 is used toadvance the carotid sheath 40 to the treatment site and to mitigate therisk of dislodging the guidewire. In procedures where the path to thetreatment site is relatively non-tortuous, an entry dilator 10 (withsufficient length to guide the carotid sheath 40 all the way to thetreatment site) can be used to fully advance the carotid sheath 40.

In some instances, the tortuous path between the entry site and thetreatment site renders the entry dilator 10 too stiff to facilitateadvancement of the carotid sheath 40. Thus, in some embodiments, apractitioner exchanges the entry dilator 10 for a tracking dilator 30,then advances the carotid sheath 40 along the tracking dilator 30.(Note: in this example, the tracking dilator 30 of FIG. 2 may be used inconnection with the same carotid sheath 40 as the entry dilator 10 ofFIG. 1. Carotid sheath 40 can thus be used in place of carotid sheath 60in connection with the tracking dilator 30.) This is done by advancingthe tracking dilator 30 and the carotid sheath 40 along the guidewire,with the tracking dilator 30 protruding from the distal end of thecarotid sheath 40. In some embodiments the tracking dilator 30 is softerthan the carotid sheath 40 and is configured to facilitate advancementof the carotid sheath 40 along tortuous paths, such as from the aorticarch to either common carotid artery or beyond. Once the carotid sheath40 is positioned, the practitioner then performs the remaining steps ofthe therapy, for example placing a stent.

In some embodiments where the entry dilator 10 is used prior to thetracking dilator 30, the slots 23, 33 are configured to allow rapidexchange of one dilator 10, 30 for the other. In some embodiments, theslots 23, 33 allow a practitioner to remove or insert a dilator 10, 30while still grasping the guidewire relatively close to the entry site.As described above, if no slot 23, 33 were present, the length of theguidewire that extends proximally from the entry site would need to belonger than the total length of the dilator 10, 30 in order to allow apractitioner to directly grasp (or otherwise secure) the guidewire whileremoving the dilator 10, 30. In some embodiments, the slots 23, 33 areconfigured to allow the practitioner to decouple the dilator 10, 30 fromthe guidewire as the dilator 10, 30 is removed from the patient's body,without the need to feed the entire dilator 10, 30 over the proximal endof the guidewire. Thus, in some instances, the “rapid exchange” natureof these dilators 10, 30 reduces the risk that exchanging dilators 10,30 will dislodge or displace the guidewire, as the practitioner is moreable to maintain the stability and position of the guidewire due to thepractitioner's ability to secure the guidewire near the entry point.

Furthermore, in some embodiments the distal end of the carotid sheath40, 60 includes a hydrophilic coating. The outer surface of the entryand/or tracking dilator 10, also includes a hydrophilic coating in someembodiments. This coating reduces friction, facilitating exchange ofdilators 10, 30 and advancement of the carotid sheath 40, 60 along thedilators 10, 30.

FIG. 5 is a longitudinal cross section of a dilator 50 disposed within acarotid sheath 70. The carotid sheath 70 includes a radiopaque markerband 72. Similar to FIGS. 1 and 2, FIG. 5 illustrates the distalportions of the dilator 50 and the carotid sheath 70; the proximal endsare not shown. Any dilator 10, 30, 50 disclosed herein may be used inconnection with any carotid sheath 40, 60, 70.

The illustrated dilator 50 is configured with a central lumen 52positioned at a radially centered position in both the distal portion ofthe dilator 50 and a main body 51 of the dilator 50, unlike the lumens(22, 32) of the entry and tracking dilators 10, 30 that areeccentrically placed (and form slots 23, 33) along a portion of thedilators 10, 30.

In some embodiments, the dilator 50 is configured with a cylindricalportion 55 adjacent the distal end of the dilator 50. This cylindricalportion 55 defines a length, L5′. L5′ is from about 3 cm to about 15 cmin some embodiments, including embodiments from about 5 cm to about 12cm and embodiments from about 7 cm to about 11 cm. Furthermore, in someembodiments, the cylindrical portion 55 is formed in a relatively thinwalled design, the wall of the dilator 50 being less than 0.025 inchesin some instances, including wall thicknesses of less than 0.020 inches,less than 0.015 inches, and less than 0.010 inches.

Further, in the illustrated embodiment, the dilator 50 includes atapered portion 54. The tapered portion 54 defines a length, L4′, fromabout 5 cm to about 30 cm, including lengths from about 10 cm to about20 cm and from about 12 cm to about 17 cm in some embodiments.Furthermore, like the tapered portion 34 of FIG. 2, in some embodimentsthe tapered portion 54 is tapered along its entire length or iscylindrical along a portion of its length and tapered along anotherportion of its length.

FIGS. 6 and 7 are transverse cross sectional views of portions of thedilator 50 of FIG. 5. FIG. 6 illustrates how the central lumen 52 may beaxially centered within the tapered portion 54, while FIG. 7 illustrateshow the central lumen 52, dilator body 51, and carotid sheath 70 may beconcentrically positioned.

In some procedures, the dilator 50 is configured for use in place ofboth the entry dilator 10 and tracking dilator 30. For instance, if apatient does not have significant scar tissue or calcification at theentry site (for example, patients who have not had prior vascularsurgery), a relatively stiff entry dilator may not be necessary. In suchinstances the dilator 50 of FIG. 5 is sufficiently stiff to allow forinitial entry and subsequent guiding of the carotid sheath 70.Additionally, the dilator 50 is sufficiently pliable, particularly asrelated to the thin walled, cylindrical portion 55, to facilitateadvancement of the dilator 50 along a difficult path for certainprocedures. This design thus obviates the need for multiple dilators andthe exchange of dilators in some instances. The dilator 50 hereindescribed may be used in place of the entry dilator 10, the trackingdilator 30, or both in any of the exemplary procedures described above.

Any of the dilators 10, 30, 50 described herein may be composed of anyelastomer or other material, including radiopaque materials such asplastics containing tungsten particles. Further, in some embodiments thedilator 10, 30, 50 is configured with a radiopaque marker bandpositioned at some point along the dilator 10, 30, 50, for example nearthe distal end. In some embodiments the radiopaque marker band is formedof a platinum alloy.

Moreover, in some embodiments any of the dilators 10, 30, 50 hereindescribed may be configured with a coating to provide lubricationbetween the dilator 10, 30, 50 and the carotid sheath 40, 60, 70 thusaiding in the advancement of the carotid sheath 40, 60, 70 along thedilator 10, 30, 50.

The examples and embodiments disclosed herein are to be construed asmerely illustrative and exemplary, and not as a limitation of the scopeof the present disclosure in any way. It will be apparent to thosehaving skill in the art with the aid of the present disclosure thatchanges may be made to the details of the above-described embodimentswithout departing from the underlying principles of the disclosureherein.

1. A dilator for use in connection with a sheath, the dilatorcomprising: an elongate main body extending from a proximal end of thedilator to a distal end of the dilator, the elongate main bodycomprising: a proximal portion extending longitudinally from theproximal end of the dilator; and a distal portion directly adjacent toand extending longitudinally from a distal end of the proximal portionof the elongate main body to the distal end the dilator; a lumendisposed within and extending longitudinally along an entire length ofthe elongate main body; a distal opening in fluid communication with thelumen, the distal opening disposed at the distal end of the elongatemain body; and a slot extending from the lumen through a sidewall of theelongate main body, the slot extending longitudinally from the proximalend of the dilator to a proximal end of the distal portion; wherein thedistal portion comprises a continuous circumference.
 2. The dilator ofclaim 1, wherein the distal portion has a continuous circumference alongan entire length of the distal portion.
 3. The dilator of claim 1,wherein the proximal portion is longer than the distal portion.
 4. Thedilator of claim 1, wherein the dilator is formed of a material having adurometer hardness of greater than 50 on the Shore D scale.
 5. Thedilator claim 1, wherein the dilator is configured to extend at least 10cm beyond a distal end of a sheath.
 6. The dilator of claim 5, whereinthe dilator is formed of a material having a durometer hardness of lessthan or equal to 45 on the Shore D scale.
 7. The dilator of claim 5,wherein the dilator includes a non-tapering cylindrical portion that issituated distal to a tapered portion of the dilator.
 8. The dilator ofclaim 7, wherein the non-tapering cylindrical portion is at least 3 cmin length.
 9. The dilator of claim 7, wherein the non-taperingcylindrical portion has a sidewall thickness of less than 0.010 inches.10. The dilator of claim 7, wherein the tapered portion adjacent thenon-tapering cylindrical portion has a length that is longer than thelength of the non-tapering cylindrical portion.
 11. The dilator of claim10, wherein the tapered portion is at least 10 cm in length.
 12. Thedilator of claim 1, wherein the slot is configured to facilitatedecoupling of the dilator from a guidewire that is disposed within thelumen of the dilator.
 13. The dilator of claim 1, wherein the dilator isconfigured to allow a first portion of a guidewire disposed within thelumen of the dilator to be extracted from the lumen of the dilatorthrough the slot while a practitioner maintains secure contact with asecond portion of the guidewire that is proximal to the first portion.14. A sheath assembly, comprising: an elongate sheath; an entry dilatorcomprising: an elongate main body extending from a proximal end of thedilator to a distal end of the dilator, the elongate main bodycomprising: a proximal portion extending longitudinally from theproximal end of the dilator; and a distal portion directly adjacent toand extending longitudinally from a distal end of the proximal portionof the elongate main body to the distal end of the dilator; a lumendisposed within the elongate main body, the lumen defining a distalopening at the distal end of the elongate main body; and a slotextending from the lumen through a sidewall of the entry dilator, theslot extending longitudinally from the proximal end of the dilator to aproximal end of the distal portion; wherein the distal portion comprisesa continuous circumference; and a tracking dilator comprising: anelongate main body extending from a proximal end of the dilator to adistal end of the dilator, the elongate main body comprising: a proximalportion extending longitudinally from the proximal end of the dilator;and a distal portion directly adjacent to and extending longitudinallyfrom a distal end of the proximal portion of the elongate main body tothe distal end of the dilator; a lumen disposed within the elongate mainbody, the lumen defining a distal opening at the distal end of theelongate main body; a non-tapering cylindrical portion adjacent thedistal end of the elongate main body; and a slot extending from thelumen through a sidewall of the entry dilator, the slot extendinglongitudinally from the proximal end of the dilator to a proximal end ofthe distal portion; wherein the distal portion comprises a continuouscircumference.
 15. The sheath assembly of claim 14, wherein the distalportion of the entry dilator and the distal portion of the trackingdilator each have a continuous circumference along their entire length.16. The sheath assembly of claim 14, further comprising a third dilator,the third dilator comprising: an elongate main body defining a distalend and a proximal end; and a lumen positioned within the elongate mainbody, the lumen defining a distal opening at the distal end of theelongate main body; a non-tapering cylindrical portion adjacent thedistal end of the elongate main body; and a tapered portion proximal ofand adjacent to the non-tapering cylindrical portion; wherein the thirddilator is formed of a material having a durometer hardness of less thanor equal to 45 on the Shore D scale.
 17. The sheath assembly of claim14, wherein the entry dilator is configured to allow a first portion ofa guidewire disposed within the lumen of the entry dilator to beextracted from the lumen of the entry dilator through the slot of theentry dilator while a practitioner maintains secure contact with asecond portion of the guidewire that is proximal of the first portion ofthe guidewire.
 18. A method of manipulating the sheath assembly of claim14 to place a sheath within the vasculature of a patient, the methodcomprising: inserting the entry dilator and sheath into the vasculatureof a patient such that a first portion of a guidewire is disposed withinthe lumen of the entry dilator and a second portion of the guidewire isdisposed proximal of the entry dilator; removing the entry dilator fromthe vasculature of the patient without removing the first portion of theguidewire from the vasculature of the patient; inserting the trackingdilator over the guidewire and into the sheath; and advancing thetracking dilator and sheath into or within the vasculature of thepatient.
 19. The method of claim 18, wherein removing the entry dilatorfrom the vasculature of the patient comprises decoupling the entrydilator from the second portion of the guidewire; and the second portionof the guidewire is not longer than the entry dilator.
 20. The method ofclaim 18, wherein removing the entry dilator from the vasculature of thepatient without removing the guidewire from the vasculature of thepatient comprises decoupling the entry dilator from the guidewire viathe slot of the entry dilator.
 21. The method of claim 18, whereinremoving the entry dilator from the vasculature of the patient withoutremoving the guidewire from the vasculature of the patient comprisesmaintaining direct contact with the second portion of the guidewirewhile the entry dilator is removed from the guidewire.
 22. The method ofclaim 21, wherein removing the entry dilator from the vasculature of thepatient without removing the guidewire from the vasculature of thepatient further comprises removing the first portion of the guidewirefrom the lumen of the entry dilator via the slot of the entry dilator.